There's a history of the Gang Show, apparently written by Ralph Reader, on this page. There is supposed to be a midi file of RIDING ALONG ON THE CREST OF A WAVE if you click on the song title about 3/4 of the way down the page.

The Gang Show seems to be primarily a British and Australian phenomenon. I had never heard of it here in the US – but then I never went further than Cub Scouts.

Wikipedia has an article.

The Gang Show has its own global web site.